WO2023156160A1

WO2023156160A1 - Method for determining the amount of at least one sealant applied to a side edge of a composite wood board

Info

Publication number: WO2023156160A1
Application number: PCT/EP2023/051871
Authority: WO
Inventors: Norbert Kalwa
Original assignee: Flooring Technologies Ltd.
Priority date: 2022-02-15
Filing date: 2023-01-26
Publication date: 2023-08-24
Also published as: EP4227668A1

Abstract

The present invention relates to a method for determining the amount of at least one sealant applied to at least one side edge of a composite wood board, comprising the following steps: recording at least one NIR spectrum of a plurality of reference samples of at least one sealant applied to a side edge of a composite wood board, wherein the at least one sealant has been applied in a known amount to the one side edge of a composite wood board, using at least one NIR probe in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm; assigning the amount applied of the at least one sealant of the reference samples to the recorded NIR spectra of the reference samples; and creating a calibration model for the correlation between the spectral data of the NIR spectra and the amounts applied of the impregnating agent of the reference samples by means of multivariate data analysis; recording at least one NIR spectrum of at least one sealant applied to a side edge, using the at least one NIR probe in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm; and determining the amount applied of the at least one sealant by comparing the NIR spectrum recorded for the sealant with the created calibration model.

Description

Method for determining the amount of at least one sealing agent applied to a side edge of a wood-based panel

The present invention relates to a method for determining the amount applied and, if necessary, the penetration of at least one sealing agent onto or into a side edge of a wood-based panel.

Description

Laminate floors have been manufactured and sold worldwide for more than twenty years. As a result, this floor covering has a more or less large market share in the floor covering segment in almost all markets worldwide. Today, a laminate floor is almost exclusively a product with a fiberboard base, which is coated with synthetic resin-impregnated paper using the so-called direct coating process. Planks are then produced from the large-format, coated panels on milling lines.

In comparison to many other floor coverings, laminate flooring benefits from its image as a wood product. However, like many other wood products, laminate flooring is sensitive to the effects of moisture or water.

This has proven to be all the more critical as more and more manufacturers have switched to so-called "glueless profiles". Here, the floor panels are provided with tongue and groove profiles on the side edges for laying into panel composites, such as laminate floors. The tongue and groove profiles allow easy laying of floor panels to floor coverings. Such tongue and groove profiles have a tongue (or tongue) in a first side edge with a (first) joining surface provided above the tongue and a groove with a lip with a (second) joining surface in a second side edge. When the panels are laid, the tongue and groove are pushed into one another so that the first and second joint surfaces come into contact. However, this approach creates a gap on top of the joined panels, and here in particular at the contact points of the joining surfaces of the two opposite side edges of two joined floor panels, through which moisture and dirt can penetrate between the floor panels. To reduce the penetration of water at the contact points of the tongue-groove profiles, modern click profiles also have a fold in the area of the joint edge. A fold is understood to mean a paragraph, an edge or a fold.

Laminate floors with so-called V-joints have also proven to be very popular. These V-joints are formed when laying floor panels with bevels. The chamfers are sloping millings on the side edges of the floor panels, which are coated with colored lacquer and give the laminate floor a visual impression that is based on parquet.

However, all of these connection variants of panels still only have insufficient protection against the ingress of water at the connection or contact point. This is due to the fact that with these products, water is sucked into the profile area through the fine joints or gaps between the floor panels via capillary forces (e.g. during cleaning) and causes swelling there. To test this problem, the so-called NALFA test was developed, in which a defined amount of water is applied to the connection area between three installed floorboards. After a defined test period (24 hours), an analysis is carried out to determine whether there is still water on the surface and whether there is any clearly visible swelling of the floorboards.

In order to improve the watertightness of the profiles, sealants have been tested to be applied to them, which are intended to remedy this deficiency. These can be sealants that only form a film and thus prevent or at least make it difficult for water to penetrate. However, it can also be agents that react with the fiberboard. This will e.g. B. described in WO 216/182896 A1, Unilin North America, LLC. There, the use of isocyanates reduces swelling and water absorption in the profile area.

However, the application of the sealing materials is difficult at the production speeds usually run on the floor lines. These speeds are more than 200 m/min on modern floor roads. The same applies to checking the order quantities. The coloring of the substances could at least enable a simple visual check, but has the problem that the decorative surface could be soiled by overspray. But even colorless sealing materials can be problematic with regard to overspray, as they can lead to large-scale soiling and/or sticking when the planks are stacked on top of each other. In addition, this control says little about the exact order quantity. Depending on what agent is used, this can also be absorbed by the quite absorbent fibreboard. This can be a problem with paraffins in particular, as these are particularly well absorbed by wood fibers (blotter effect). This problem can be more or less severe depending on the density of the fiberboard. The type of wood fiber can also play a role.

Planks could of course be removed from the milling lines at regular intervals and examined. However, significant quantities may have been produced between the last and the current withdrawal. In addition, a purely visual check would not be conclusively meaningful due to the absorbency of the fibreboard.

The consequent disadvantages are, inter alia, difficult control of the application amount of the sealant, high machine speed, strong influence of the fiberboard. In addition, continuous analysis is not possible.

The invention is therefore based on the technical task of checking the application quantities of the sealing material on the side edges, in particular on profile surfaces, joining surfaces and/or chamfers of side edges, of wood-based panels and its distribution as continuously as possible non-destructively. If possible, this should be possible for a large number of sealing agents without having to use different measuring systems. Also, a measurement should not only be able to detect the sealing material directly on the surface, but also material that has penetrated the fiberboard. The measurement should not be spatially demanding and should not experience any restrictions due to the on-site conditions (dust). Switching from one sealing material to another should be possible quickly in view of the measurements.

This object is achieved by a method having the features of claim 1.

Accordingly, a method is provided for determining the application quantity of at least one sealing agent or impregnating agent on at least one side edge, in particular on profile surfaces, joining surfaces and/or chamfers of side edges, of a wood-based panel, preferably a floor panel. This procedure includes the following steps: - Recording of at least one NIR spectrum of several reference samples of at least one sealing agent applied to a side edge of a wood-based panel, wherein the at least one sealing agent was applied to a side edge of a wood-based panel with a known amount, using at least one NIR measuring head in one Wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm, or also preferably between 1150 and 1250 nm and/or between 1350 nm and 1650nm;

- Allocation of the application quantity of the at least one sealing agent of the reference samples to the recorded NIR spectra of the reference samples; and

- Creation of a calibration model for the connection between the spectral data of the NIR spectra and the applied amounts of the impregnating agent of the reference samples using a multivariate data analysis;

- Recording of at least one NIR spectrum of at least one sealing agent applied to a side edge using the at least one NIR measuring head in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm , even more preferably between 1200 nm and 1700 nm, or also preferably between 1150 and 1250 nm and/or between 1350 nm and 1650 nm; and

- Determining the application quantity of the at least one sealing agent by comparing the NIR spectrum recorded for the sealing agent with the calibration model created.

According to the present method, the application quantity of the sealing agent is determined by an NIR measurement in the areas of the profile exposed to the sealing materials (in particular the profile areas near the surface), the joint surfaces and/or chamfers of the side edges of wood-based panels. A wide variety of sealing materials can be detected and quantitatively evaluated. As described in detail later, the sealing agents used are film-forming compositions that are preferably made from non-crosslinked materials or components exist. In particular, no curable formaldehyde-containing resins are used as side edge sealants.

In addition, NIR spectroscopy also offers the possibility of detecting sealing agent that has penetrated the fiber board at the side edges. This can occur not only with paraffin but also with materials that have a low viscosity. The detection of sealant in the surface of the plate is e.g. B. with IR spectroscopy or other spectroscopic methods is not possible.

In addition to determining the amount applied (and distribution) of the at least one sealing agent on a side edge of a wood-based panel, the present method also makes it possible to determine the penetration of the

Sealant (e.g. the penetration depth of the sealant) into the side edge of the at least one wood-based panel. The determination of the penetration of the

Sealant in the wood-based panel is particularly advantageous for low-viscosity sealants or sealants with a high water content.

In one embodiment of the present method, the recorded NIR spectrum, in combination with an examination of the percentage of penetration of the sealing agent into the side edge, thus enables a correlation to the penetration depth. Surprisingly, it has been shown that, depending on how far the sealing agent penetrates into the side edge, a signal increase can be observed for the main peak of the respective sealing agent.

It is known from the prior art (e.g. WO 2020/016176 A1) to use NIR spectroscopy to measure a melamine-formaldehyde resin layer which is applied to the planar surface of wood-based panels, but not to the side edges of wood-based panels. However, the coating of a narrow surface/profile/bevel of a wood-based panel and the measurement of a sealing layer applied to a narrow surface/profile/bevel pose a greater technical challenge with a greater susceptibility to errors than the coating of a surface.

In addition, the planar surface and side edges of wood-based panels differ in that the surface of the wood-based panels has a pressed skin due to the pressing, which at least makes it difficult for liquid to penetrate, while such a pressed skin does not exist on the side edges, so that liquid can more easily can be added to the side edges of the wood-based panels. Rather, the side edges of wood-based panels are porous, which allows penetration of the sealant applied to the side edges.

Due to the pressing process, wood-based panels also have a lower bulk density in the central area of the panel than on the planar surface of the panel, which has a much higher bulk density. Correspondingly, a liquid, such as a sealant, can penetrate much better into the panel at the side edges in the central panel area than at the panel surface. This problem is not mentioned in WO 2020/016176 A1, since only one layer applied to the planar surface of a wood-based panel is measured here.

The present measurement method also takes into account the high production speeds, which place significantly higher demands on the analysis than a slow-running system. The speed of a production system, in particular a system for applying a sealing agent to a side edge, is between 100 and 250 m/min, preferably between 120 and 200 m/min, particularly preferably between 150 and 180 m/min. The measurement along the side edge of a wood-based panel, in particular in the form of a plank, is carried out at at least one, preferably at 3-4 different measuring points. Since several scans per second are carried out with NIR spectroscopy, this means that with a system speed of the milling line of, for example, 200 m/min (3.3 m/sec) and a measuring frequency of 8 NIR measurements/sec, it is ensured that each passing plank is measured several times.

The advantages resulting from the present method are, among other things, the possibility of an on-line measurement, analysis of different sealing materials, quick correction, determination of the total application, no coloring of the sealing material necessary.

According to the present method, an NIR spectrum of the side edge of the wood-based panel coated with the sealing agent is recorded. NIR radiation is generated and directed onto the coated surface of the sample to be analyzed, where the NIR radiation interacts with the components of the sample and is reflected or scattered. An NIR detector captures the reflected or scattered NIR radiation and generates an NIR spectrum that contains the desired chemical information about the sample. With this measurement, a large number of individual NIR measurements are carried out in one second, so that statistical validation of the measured values is also guaranteed. The NIR spectroscopy together with multivariate data analysis (described below) offers a possibility to establish a direct relationship between the spectral information (NIR spectra) and the parameters to be determined of the applied sealant.

First, reference samples of a wood-based panel are provided, the side edge of which is provided with the respective sealing agent. It is essential that the reference sample is similar to the sample to be measured; i.e. in particular the sealing agent and wood-based panel with the side edge to be coated of the reference sample have the same composition as the sample to be measured. The similarity of the sample to be measured and the reference sample is essential, especially when using sealing agents with solvents and possibly other additives.

From these reference samples, at least one NIR spectrum in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm, or also preferably between 1 150 nm and 1250 nm and/or recorded between 1350 nm and 1650 nm.

The respective application quantity of the at least one sealing agent of the reference samples is then assigned to the recorded NIR spectra of these reference samples, and a calibration model for the relationship between the spectral data of the NIR spectra of the reference samples and the associated parameter values (application quantity) is created using a multivariate data analysis created; i.e. an NIR spectrum of the reference sample corresponds to each parameter value of the reference sample. The calibration models created for the various parameters are stored in a suitable data memory.

At least one sealing agent is then applied to a side edge of a wood-based panel, and at least one NIR spectrum of the applied sealing agent is recorded. The desired parameters of the sealing agent (here the amount applied and, if necessary, the depth of penetration into the side edge) can then be determined by comparing the NIR spectrum recorded for the sample with the calibration model created. It is thus possible to simultaneously determine several parameters of interest of the applied sealing agent from a single NIR spectrum determined for the sample to be measured by an automated comparison or adjustment with the calibration models created for the respective parameters.

It makes sense to compare and interpret the NIR spectra over the entire recorded spectral range. This is advantageously carried out using a multivariate data analysis (MDA) known per se. In the case of multivariate analysis methods, typically several statistical variables are examined simultaneously in a manner known per se. For this purpose, with these methods, the number of variables contained in a data set is usually reduced without reducing the information contained therein at the same time.

In the present case, the multivariate data analysis is carried out using the method of partial least squares regression (partial regression of the smallest squares, PLS), which allows a suitable calibration model to be created. The evaluation of the data obtained is preferably carried out using suitable analysis software such as, for example, the analysis software SIMCA-P from Umetrics AB or The Unscrambler from CAMO.

In another embodiment, spectral data from the NIR spectral range between 1150 and 1250 nm and/or between 1350 and 1650 nm is used to create the calibration model, which is pretreated using suitable mathematical methods and then fed to the multivariate data analysis .

The importance of a wavelength for the prediction of parameters of the applied sealant, such as application amount and penetration, from the NIR spectrum is shown with the help of the regression coefficients. The regions with large coefficients have a strong influence on the regression model. The representation of the regression coefficients in a PLS regression model for the determination of the sealant shows that the wavelength range between 1150 and 1250 nm and/or between 1400 nm and 1600 with a maximum at 1490 nm is most important for the calculation of the model, since here the magnitudes of the regression coefficients are largest. Although the other areas in the spectrum have less information content in relation to the NIR measurement, they still help to take into account or minimize the additional information or disruptive influencing variables. In order to eliminate disruptive influences (e.g. partially rough texture of the surface of the side edges of the wood-based panel), it is necessary to preprocess the spectral data using mathematical methods (e.g. derivative data pretreatment, standardization according to SNVT (Standard Normal Variate Transformation), multiplicative signal correction (EMSC, Extended Multiplicative Signal Correction, etc.) The baseline effects, which are mainly caused by the different color of the samples, are removed from the spectra, overlapping bands are separated from each other and the dependence of the light scattering at the substrate surface is taken into account data pretreatment is preferred to reduce light scattering on the rough surface of the substrate In measurement, calibration and data pretreatment focus on baseline shift removal.

From the pre-treated data, a calibration model is developed with the help of multivariate data analysis, which includes all aspects used in the calibration.

Accordingly, the comparison and the interpretation of the NIR spectra preferably take place in the spectral range between 1150 and 1250 nm and/or between 150 and 1650 nm using the multivariate data analysis MDA. In the case of multivariate analysis methods, typically several statistical variables are examined simultaneously in a manner known per se. To do this, the number of variables contained in a data set is reduced without reducing the information contained therein at the same time.

The present method makes it possible to provide the measured values in a short time (online, preferably without a disruptive time delay) compared to conventional (known) measuring methods. The measurement data can be used for quality assurance, research and development, for process control, regulation, control, etc. The measuring process does not reduce the production speed, etc. Basically, this improves the monitoring of production. In addition, downtimes are reduced through quality determinations and system adjustments.

The advantages of the present method are manifold: non-contact multi-parameter determination (“real time” or “real-time” measurement) with a significantly reduced time delay in the evaluation of the measured parameter values; improved system control or regulation, reduction in rejects, improvement in the quality of the products manufactured on the system, improvement in system availability. In one embodiment of the present method, the at least one wood-based panel is a medium-density fiber (MDF), high-density fiber (HDF) or coarse particle board (OSB), plywood panel or a wood-plastic panel (WPC).

The width of the side edge to be coated with the sealing agent is between 2.5 and 3.5 mm, preferably 3 mm.

In one embodiment, the at least one sealing agent has a solids content of between 30 and 100% by weight, preferably between 50 and 100% by weight, in particular between 70 and 100% by weight. The sealing agent is preferably in the form of a suspension, in particular an aqueous suspension. In a preferred embodiment, aqueous suspensions with a solids content of 50-70% by weight and a water content of 30-50% by weight are used.

In a further embodiment, the at least one sealing agent is used in an amount of between 0.1 g/lfm and 1.5 g fl/lfm, preferably between 0.2 and 1.5 g fl/lfm, particularly preferably between 0.25 and 0 .75 g fl/lfm, e.g. preferably of 0.5 g fl/lfm is applied to the side edge.

A composition comprising at least one compound of general formula (I) SiX ¹ 4 where X ¹ is alkoxy, aryloxy, acyloxy, at least one compound of general formula (II) R ² bSiX ² <4-b), wherein X ² is H or alkoxy, aryloxy, acyloxy, R ² is a non-hydrolyzable organic radical R ² is selected from the group consisting of alkyl and aryl, and b = 1, 2, 3, or 4, and at least one aqueous polymer dispersion. Such a composition is described in WO2020/016176 A1,

This silane-containing sealant allows the pores present in the wood fiber board to be filled and encapsulated around the wood fibers, thereby "sealing" them. On the other hand, the use of hydrophobic modifications creates a "hydrophobic treatment" of the remaining pores and the uncoated wood fibers. In order to obtain the highest possible flexibility of the coating, the silane compounds are mixed with a suitable, aqueous polymer dispersion. The polymers used have functional groups that are compatible with the inorganic silane matrix. It is therefore possible to produce a coating with a high degree of crosslinking even at low temperatures. The radical X ¹ is more advantageously selected from a group containing Ci-6-alkoxy, in particular methoxy, ethoxy, n-propoxy and butoxy, Ce-w aryloxy, in particular phenoxy, C2-7-acyloxy, in particular acetoxy or propionoxy, and the rest X ² is advantageously selected from a group containing H, Ci-6-alkoxy, in particular methoxy, ethoxy, n-propoxy and butoxy, Ce-w aryloxy, in particular phenoxy, C2-7-acyloxy, in particular acetoxy or propionoxy,

In a particularly preferred variant of the silane-containing sealing agent, the compound of the general formula (I) corresponds to the formula SiX ¹ 4, where the radical X ¹ is alkoxy, in particular methoxy, ethoxy, n-propoxy or i-propoxy. Tetramethoxysilane and tetraethoxysilane are used as particularly preferred crosslinkers.

In a further embodiment of the silane-containing sealing agent, the non-hydrolyzable organic radical R ² of the compound of the formula (II) is selected from a group comprising CrCis-alkyl, in particular Ci-Ci ₀ -alkyl, and Ce-C -aryl. These can be unsubstituted or substituted with another hydrophobic group. It is preferred if the non-hydrolyzable organic radical R ² is selected from the group containing methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl , cyclohexyl, phenyl and naphthyl. Methyl, ethyl, propyl, octyl or phenyl radicals are particularly preferred.

In particular, the compound of formula (II) may include one of the following formulas:

- R ² 4Si with R ² as a C1 -C5 alkyl group, preferably methyl or ethyl such as tetramethylsilane;

- R ² sSiX ² with R ² as a C1 -C5 alkyl group, preferably methyl or ethyl and with X ² as H, such as trimethylsilane,

- R ² SiX ² 3 with R ² as a C1 -C10 alkyl group, preferably methyl, ethyl, propyl, pentyl, hexyl, heptyl, octyl, or as a C6-C10 aryl group, preferably phenyl and with X ² as alkoxy , In particular methoxy, ethoxy, n-propoxy or i-propoxy, such as octyltriethoxysilane, phenyltriethoxysilane.

In a variant of the silane-containing sealing agent, a compound of general formula (I) and a compound of general formula (II) are used as additives. In a further variant of the silane-containing sealing agent, however, at least one compound of the general formula (I) and at least two, preferably at least three, compounds of the general formula (II) can also be present in the additive. Any combination is conceivable here.

In a further embodiment of the silane-containing sealing agent, the at least one polymer is selected from the group consisting of polyurethanes, epoxy resins; and polyacrylates. The use of a polyurethane polymer is preferred here, the polyurethane polymer being based on aromatic polyisocyanates, in particular polydiphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI) and/or diphenylmethane diisocyanate (MDI), PMDI being particularly preferred. The polymer is incorporated into the network formed from the silane compounds and gives the composition flexible properties that facilitate application.

A silane with hydrophobic radicals such as trimethylsilane, phenyltriethoxysilane and octyltriethoxysilane is preferably used in a mixture with another (hydrophilic) silane such as tetraethoxysilane (WO 2020/016176 A1). Alcohols, in particular ethanol, or water are used as solvents. In this case, the solids content of the sealing agent used is 50% by weight.

In a further embodiment of the silane-containing sealing agent, at least one phase color is added to the mixture of silanes and polymer dispersion. Such a sealant is used in particular for coating fibers.

In another embodiment, the at least one phase color used in the present composition comprises color pigments and an aqueous solvent or suspending agent. Carbon black, iron oxides, titanium dioxide and/or organic pigments are used as color pigments. Suitable solvents or suspending agents are melamine resin formaldehyde resins or acrylates. In one embodiment, the bevel color includes color pigment, acrylate, and water.

In a further embodiment, the at least one phase color used comprises color pigments and an aqueous solvent or suspending agent. Carbon black, iron oxides, titanium dioxide and/or organic pigments are used as color pigments. Suitable solvents or suspending agents are melamine resin formaldehyde resins or acrylates. In one embodiment, the bevel color includes color pigment, acrylate, and water.

The silane-containing sealing agent, in particular the composition of silanes, polymer dispersion and phase color, has a viscosity (measured according to EN ISO 2431: 201 1, coating materials - determination of the flow time with flow cups, 21 ° C) with a flow time between 20 and 100 seconds, preferably between 30 and 80 seconds, particularly preferably between 35 and 60 seconds, over a period of at least 30 minutes, preferably at least 60 minutes, particularly preferably at least 120 minutes.

In a further embodiment, at least one isocyanate is used as the sealing agent. Preferred isocyanates are polydiphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI) and/or diphenylmethane diisocyanate (MDI). The use of diphenylmethane diisocyanate (MDI) is particularly preferred. MDI is preferably applied at 100% solids.

It is possible to use the isocyanate alone or in combination with other sealing agents. For example, a mixture of MDI and an epoxy resin and acetic anhydride can be used. Acetic anhydride causes acetylation of the wood fibers, making the wood fibers less susceptible to moisture.

It is also possible for the at least one isocyanate to comprise at least one solvent as the sealing agent. Suitable solvents are water, a glycol ether such as dipropylene glycol dimethyl ether, ethyl acetate, propyl acetate, butyl acetate, acetone, butyl diphenyl methane, tetramethoxy ether, benzoic acid ester. The use of hydrophobic solvents such as propyl acetate, diphenylmethane and diphenylethane has proven particularly advantageous. The proportion of the solvent is 10-40% by weight, preferably 15-30% by weight.

In a further embodiment, a UV lacquer, in particular a monomer-free UV lacquer, can be used as the sealing agent. A suitable UV varnish would be a water based copolymer of ethylene acrylic acid. Such products form a stable hydrophobic layer.

In yet another embodiment, a hot melt adhesive can be used as the sealant. Suitable hot melt adhesives are polypropylene (PP), Polysulfone, polyurethane (PUR), polyetherimide and/or polyolefin. The hot melt adhesives are applied at temperatures between 150 and 200°C.

It is also possible to use paraffin as a sealing agent. Paraffin is a mixture of acyclic alkanes (saturated hydrocarbons) with the general molecular formula CnHsn+s with n between 18-32 and can be used as liquid or solid. The paraffin is preferably applied to the side edges as an emulsion with a solids content of 50% by weight.

As already indicated above, the sealing agents to be applied to the side edges of wood-based panels are compositions which preferably form a film on the side edge. In a preferred form, these compositions consist of at least two or three or more components which are present in non-crosslinked form before application. The precursors contained in the composition are measured accordingly. This applies in particular to the silane-containing sealants described above.

If mixtures of different components are used, aqueous suspensions are often used here, e.g. with a water content of 50% by weight. However, the measurement of suspensions with a high water content using NIR spectroscopy is not trivial, since the water signal (at approx. 1450 nm) in the NIR spectrum partially superimposes the NIR signals of the deficit components essential for the film formation of the sealing agent and makes a meaningful evaluation more difficult . Accordingly, the present method requires careful analysis of the determined NIR spectrum.

As previously mentioned, formaldehyde resins such as melamine-formaldehyde resin or urea-formaldehyde resin, which are typically used to coat the planar surface of engineered wood panels and impregnate paper plies, are not used as side edge sealants herein. Consequently, no resins which harden or can be hardened, in particular by condensation or polycondensation reactions, are used as sealing agents.

The sealing agent can be applied to the edges of the wood-based panels, for example by spraying with a spray system, rollers, transfer printing or using a Vakkumat and transfer wheel. Suitable vacuum data for overspray-free, profile-independent vacuum coating or partial coating of profile elements distributed by Schiele (Vacumat®). Transfer wheels allow bevels to be coated (TransferDisc from Schiele).

As already indicated, the sealant is applied in particular to the side edges of floorboards. The floorboards used here preferably have the following formats: length between 1200 and 2000 mm, preferably between 1300 and 1500 mm, particularly preferably between 1350 and 1400 mm, such as 1375 mm, 1380 mm, 1875 mm; Width between 100 and 300 mm, preferably between 150 mm and 250 mm, particularly preferably between 180 and 200 mm, such as 157 mm, 188 mm, 193 mm, 244 mm. Typical formats are 1380 x 193 mm; 1380x244mm; 1380x157mm; 1375x188mm; 1875x244mm.

The format size of the planks, in combination with the line speed (200 m/min), plays a major role in the development of a measuring method suitable for side edges. The NIR measurements are taken eight times per see. This means that a measurement is taken about every 40 cm on a plank (3 - 4 measurements per side edge per plank). This ensures that fluctuations in the application (plank inflow Z outflow) can be detected. Any other, slower analysis than the NIR spectroscope used here could not cope with this task.

The layer thickness of the sealing agent on the side edge can be in a range between 10 and 50 μm, preferably between 20 and 40 μm. However, it is also possible that the layer thickness of the sealing agent on the side edge is less than 10 μm, since the sealing agent has largely penetrated into the wood-based panel.

The wood-based material boards used here can have different binder systems, which are mixed and pressed with the wood fibers or wood particles as binders. Preferred binder systems are: formaldehyde resins, such as urea-formaldehyde resins, melamine-formaldehyde resins, melamine-urea-formaldehyde resins; Polyurethanes, preferably based on polydiphenylmethane diisocyanate (PMDI), epoxy resin or polyester resins.

The present wood-based material panels can also have a coating on the upper side of the panel with foils, eg foils made from thermoplastic materials such as PVC or PP, or paper layers, such as decorative paper layers or overlay papers. Particularly preferred wood-based panels, especially in the form of floorboards, are:

- HDF board with urea-formaldehyde glue

- HDF panel with urea-formaldehyde glue and foil, such as PVC foil, glued to at least one top side of the panel;

- HDF board with melamine-urea-formaldehyde glue;

- HDF board with PMDI glue, and

- WPC board with glued film, such as Polypropylene (PP) film.

In a further embodiment, it is provided that the side edge of the wood-based material board to be provided with the sealing agent and a side edge lying opposite it comprise mechanical coupling means which enable the wood-based material board to be coupled or connected to similar wood-based material boards, forming a composite (panel composite).

The mechanical coupling means are preferably provided in the form of a groove and a tongue. For example, a floor panel for realizing a floor covering is known from EP 1026341 B1, coupling parts in the form of a groove and a tongue being provided on the edges of two opposite sides of the panels. Tongue and groove are designed in such a way that when two or more floor panels are in the assembled state, a clamping force is exerted on one another, which forces the floor panels together. The clamping force is caused by an elastically bendable lip in the groove, which is at least partially bent in the assembled state and in this way provides the aforementioned clamping force.

In a further variant, the NIR measurement can take place both online and offline.

The present method is carried out in a production line comprising at least one NIR multi-measuring head, preferably at least two NIR multi-measuring heads, particularly preferably at least four measuring heads (two measuring heads for the longitudinal edges and two measuring heads for the transverse edges) and at least one control system. Such a production line can be a production line for the production of material panels. The present method for determining the amount of sealing agent applied to the side edges is preferably carried out continuously and online.

The control system of the production line comprises at least one computer-aided evaluation unit (or processor unit) and a database. Takes place in the evaluation unit the alignment or comparison of the NIR spectrum measured for the product (ie side edges coated with the sealant) with the calibration models created for the individual parameters in each case. The parameter data determined in this way are stored in the database.

The data determined with the present spectroscopic method can be used to control the production line. The non-contact measured parameter values of the NIR multi-measuring head ("actual values") can, as already described, be used directly and in "real time" for the control or regulation of the relevant system, for example by using the measured and stored in the database, e.g. a relational database, actual values are stored and compared with the target values of these parameters that are available there. The resulting differences are then used to control or regulate the production line.

A computer-implemented method and a computer program comprising instructions which, when the program is executed by a computer, cause the computer to execute the computer-implemented method are provided for the adjustment and control of the production line. The computer program is stored in a storage unit of the production line control system.

The invention is explained in more detail below with reference to the figures of the drawings using an exemplary embodiment. It shows:

FIG. 1 NIR spectra of various sealing agents applied to a side edge or a bevel of a wood-based panel;

FIG. 2 NIR spectra of paraffin as sealing agent applied to a side edge of a wood-based panel;

FIG. 3 NIR spectra of paraffin in various amounts as sealing agents applied to a side edge of a wood-based panel before heating;

FIG. 4 NIR spectra of paraffin in various amounts as sealing agents applied to a side edge of a wood-based panel after heating, and FIG. 5 NIR spectra of a mixture of silane, polymer dispersion and bevel color as sealing agents applied to a side edge of a wood-based panel.

Exemplary embodiment 1:

Sealing materials were applied to a glueless floor profile in a continuous process on the tongue side in the area below the decor in a width of approx. 3 mm and over the entire length of the plank. The sealing materials were paraffin, aromatic isocyanates (MDI®) and aliphatic chain silanes (trimethylsilane, phenyltriethoxysilane and octyltriethoxysilane in a mixture with tetraethoxysilane). The same sealing material was also applied to the groove side in a width of 3 mm and over the entire length of the plank below the decor. This was done on the long and short sides.

The amount applied was approx. 0.5 g sealing agent fl. / Ifm. Except for the isocyanate-containing sealant, which had a solids content of 100%, the other sealants had a solids content of about 50%. The planks were subjected to intermediate drying with hot air.

A spectrum of the area provided with sealing material was then created in the run with an NIR measuring head. This was repeated on other planks using different sealing materials. A blank with no sealing material was also measured.

As can be seen from the diagram in FIG. 1, even chemically very different compounds are detected. This is surprising since the sealing materials are chemically very different compounds.

The NIR spectra of the sealing ^materials show clear bands (methyl-zmethylene groups) in the range of approx the range around 1200 - 1220 nm (8333 - 8200 cm ^-1 ) can be considered for the evaluation.

On a glueless floor profile, sealing materials were applied to the bevel on the tongue side over a width of approx. 3 mm and over the entire length of the plank. The sealing materials were paraffin, aromatic isocyanates (MDI) and aliphatic chain silanes (trimethylsilane, phenyltriethoxysilane and octyltriethoxysilane in a mixture with tetraethoxysilane). The same sealing material was also applied to the bevel on the groove side in a width of 3 mm and over the entire length of the plank. This was done on the long and short sides.

Example 3:

On a glueless floor profile, paraffin emulsion was applied as a sealing material in a continuous flow on the tongue side in the area below the decor in a width of approx. 3 mm and over the entire length of the plank. The emulsion had a solids content of about 50%. The paraffin was also on the groove side in a width of 3 mm and over the entire Plank length applied below the decor. This was done on another plank with the same application quantity. It turned out that with both planks a paraffin film could be felt and seen on the surface of the plank.

Both planks were subjected to intermediate drying with hot air. One of the two planks was treated with a hot air gun until the paraffin on the surface could no longer be felt. This was done on the long and short sides. A spectrum of the area provided with sealing material was then created in the run with an NIR measuring head. A blank with no sealing material was also measured.

As can be seen from the diagram in FIG. 2, the paraffin that had essentially migrated into the fiberboard as a result of the treatment was still detected.

Example 4:

On a glueless floor profile, paraffin emulsion was applied as a sealing material in a continuous flow on the tongue side in the area below the decor in a width of approx. 3 mm and over the entire length of the plank. The emulsion had a solids content of about 50%. The paraffin was also applied to the groove side in a width of 3 mm and over the entire length of the plank below the decor. This was done with different application amounts on several planks. The amounts applied were approx. 0.25, 0.5 and 1 g paraffin emulsion fl./ifm. It turned out that with the last two application quantities, a paraffin film could be felt on the surface of the plank.

All planks were subjected to intermediate drying with hot air. A set of samples with the same application amounts was heated with a hot air gun after application until the paraffin had penetrated the fiber board. This was done on the long and short sides. A spectrum of the area provided with sealing material was then created in the run with an NIR measuring head. A blank sample without sealing material was also measured in each case.

As can be seen from the diagrams in FIGS. 3 and 4, the quantity gradation was recorded. This shows that even very small order quantities can be reliably recorded.

Preparation of a first silane-containing sealing composition:

12.3 g octyltriethoxysilane, 2.4 g trimethylsilane, 6.1 g phenyltriethoxysilane, 20.8 g tetraethoxysilane and 28.8 g of an aqueous SiOs dispersion (50% by weight) from Obermaier are initially charged, heated to 80° C. and stirred, 3.6 g of para-toluic acid in water (30% by weight) are then added with stirring, and the mixture is stirred for 120 minutes. After a further 24 hours, the pH is raised to a pH of 7 by adding a 25% strength ammonia solution (6.2 g in the above example) while stirring.

After a further stirring time of 2 hours, 80 g of water are then added, the mixture is stirred again for 30 minutes and the suspension is then stored for 4 hours without stirring.

After this waiting time, the aqueous phase with the binder component separates from the ethanolic phase. The aqueous phase is now separated using a separating funnel. The inorganic aqueous coating system is thus obtained.

50 g of this coating system (solids: 52%) is then mixed with 20 g of an aqueous polyurethane solution (from Alberdingk U 3251, solids: 35%).

The coating system can now be applied to an edge with a foam roller or pipette.

A spectrum of the area provided with sealing material was then created in the run with an NIR measuring head. A blank sample without sealing material was also measured in each case.

Preparation of a second silane-containing sealing composition:

Preparation of dispersion A)

28.8 g of an aqueous SiO 2 dispersion (Köstrosol 3550) and 20 g of an aqueous Alberdingk U 3215 polyurethane solution are initially taken. Preparation of solution B)

In parallel, 12.3 g of octyltriethoxysilane, 2.4 g of trimethylsilane, 6.1 g of phenyltriethoxysilane, 20.8 g of tetraethoxysilane and 28.8 g of water are heated to 50° C. and stirred, and 2.8 g of sulfuric acid are then stirred and stirred for 120 minutes . This solution is then stirred into the above suspension in the warm state and stirred at room temperature for a further 60 minutes. A 0.1 molar NaOH solution is added until a pH of 7.5 is reached.

After standing for 24 hours, the alcoholic phase is separated off using a separating funnel.

The additive (Inosil AS) can now be added up to 50% by weight to a commercially available bevel colour, which remains stable for several weeks. Curing after application takes place thermally (e.g. 100 °C, 5 minutes).

The mixture of bevel color and silane additive (Inosil AS) was applied to a glueless floor profile in a continuous flow on the tongue side in the area below the decor in a width of approx. 3 mm and over the entire length of the plank as a sealing material. The mixture of bevel color and silane additive was also applied to the groove side in a width of 3 mm and over the entire length of the floorboard below the decor.

This was done on several boards with different application amounts (see Table 1).

As can be seen from the diagram in FIG. 5, the quantity gradations were recorded. This shows that even very small order quantities can be reliably recorded. The differences in the order quantities can be found in at least two places in the spectrum Evaluate the NIR spectrum (1150 to 1250 nm and 1350 to 1650 m). A malfunction (blank sample) is also easily recognizable.

Claims

Expectations

1. A method for determining the application quantity of at least one sealing agent on at least one side edge of a wood-based panel, in particular a floor panel, comprising the steps

- Recording of at least one NIR spectrum of several reference samples of at least one sealing agent applied to a side edge of a wood-based panel, wherein the at least one sealing agent was applied to a side edge of a wood-based panel with a known amount, using at least one NIR measuring head in one Wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm,

- Recording of at least one NIR spectrum of at least one sealing agent applied to a side edge using the at least one NIR measuring head in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm , more preferably between 1200 nm and 1700 nm,

- Determining the application quantity of the at least one sealing agent by comparing the NIR spectrum recorded for the sealing agent with the calibration model created, - wherein no curable formaldehyde resins are used as sealants. Method according to Claim 1, characterized in that the side edges have profile surfaces, joining surfaces and/or chamfers to which the sealing agent is applied. Method according to one of the preceding claims, characterized in that the penetration of the sealing agent into the side edge of the at least one wood-based panel is determined. Method according to one of the preceding claims, characterized in that the at least one wood-based panel is a medium-density fiber (MDF), high-density fiber (HDF) or coarse particle board (OSB), plywood panel or a wood-plastic panel (WPC). Method according to one of the preceding claims, characterized in that the at least one sealing agent is an isocyanate, in particular methylene diphenyl isocyanate (MDI), toluylene diisocyanate (TDI), a fluorocopolymer, in particular perfluoroalkyl methacrylic copolymer, an epoxy resin, acetic anhydride, paraffin. A method according to any one of claims 1-4, characterized in that the at least one sealing agent is a mixture of at least one compound of the general formula (I) SiX ¹ 4 where X ¹ is alkoxy, aryloxy, acyloxy, at least one compound of the general Formula (II) R ² bSiX ² <4-b) where X ² is H or alkoxy, aryloxy, acyloxy, R ² is a non-hydrolyzable organic radical R ² is selected from the group comprising alkyl and aryl, and b = 1, 2, 3, or 4, at least one aqueous polymer dispersion and optionally at least one phase color. Method according to one of the preceding claims, characterized in that the at least one sealing agent comprises at least one solvent. Process according to Claim 7, characterized in that the at least one solvent is water, a glycol ether such as dipropylene glycol dimethyl ether, ethyl acetate, acetone, butyl diphenyl methane, tetramethoxy ether

9. The method according to any one of the preceding claims, characterized in that the at least one sealing agent has a solids content of between 30 and 100% by weight, preferably 50 and 100% by weight.

10. The method according to any one of the preceding claims, characterized in that the at least one sealing agent is present in an amount of between 0.2 and 1.5 g fl/lfm, preferably between 0.25 and 1 g fl/lfm, particularly preferably 0 5 g fl/lfm is applied to the side edge.

11 . Method according to one of the preceding claims, characterized in that spectral data from the entire recorded spectral range are used to create the calibration model.

12. The method as claimed in one of the preceding claims, characterized in that spectral data from the NIR spectral range between 1150 and 1250 nm and/or between 1350 nm and 1550 nm are used to create the calibration model and are pretreated using suitable mathematical methods and then fed into the multivariate data analysis.

13. The method according to any one of the preceding claims, characterized in that the determination of the application amount and / or penetration of the sealing agent in the side edge of the wood-based panel is carried out continuously and online.

14. The method according to any one of the preceding claims, characterized in that the side edge of the wood-based material board to be provided with the sealing agent and a side edge opposite thereto comprise mechanical coupling means which enable the wood-based material board to be coupled or connected to similar wood-based material boards, forming a composite (panel composite). .

15. The method according to claim 14, characterized in that the mechanical coupling means are provided in the form of a groove and a spring.